This invention is generally related to equipment used for paying off tape into a process. More particularly, the invention is related to automatically performing a xe2x80x9ccrossoverxe2x80x9d, i.e. transitioning from a running tape to a new tape.
The process of manufacturing of electrical and optical cable (having one or more filaments or conductors) often requires that tape be continuously pulled in and folded or wrapped around a cable component. For instance, in the manufacture of electrical shielded cable, the tape material is a pliable metallic foil that is pulled in by the core of the cable and is wrapped around the core in a helical manner as the continuously manufactured part is rotating. Other tape materials include paper, plastic, and metallized plastic. In other instances, such as an extrusion for cable jacketing, the tape does not rotate but rather forms a xe2x80x9ccigarette wrapxe2x80x9d around the manufactured part. The tape itself may be supplied as a flat roll whose width is the same as the tape width, sometimes called a pancake pad. Another tape packaging configuration is a wide roll where the tape is traversed, or oscillated, back and forth while being wound onto a center tube. Both types of rolls have a center tube which is typically of cardboard or plastic and enables mounting the roll onto tape payoff equipment.
In the tape payoff equipment, the roll is mounted on a shaft which is attached to a brake or a motor to apply positive or negative torque on the roll as the tape is being pulled out by the manufacturing process. When the roll is about to be emptied, a crossover to a new roll must be performed, preferably without slowing or stopping the process.
One technique for achieving crossover without stopping the process uses the following mechanism. Two tape positions are provided, one of which is running and the other is available for the crossover. The running tape has an in-line accumulator, generally in the form of a narrow box where the tape is folded back and forth in a serpentine form. The accumulation is maintained by supplying a length of tape continuously, equal to the length of tape being pulled out of the box. When the time for a changeover arrives, a clamp is applied to the upstream portion of the accumulation. Thus, the tape being fed into the process is now being sourced by the accumulation which is gradually being depleted due to the clamp being applied to its upstream portion. A human operator is given a limited amount of time to perform a manual joining of the clamped end of the running tape to the leading edge of tape from a new roll. This joining must be performed before the accumulation has been completely depleted, otherwise there will be an interruption in the feeding of tape to the process (and the tape will brake). The amount of time available for this manual joining depends on the amount of accumulation and on the line speed of the tape, i.e. the speed at which the tape is being pulled in by the manufacturing process. For certain high speed processes, the line speed must be lowered temporarily to allow this crossover. In addition to the presence of the operator being required at the right moment, the operator must also have a certain degree of agility and skill to perform the manual joining in the limited period of time.
Other tape payoff operations do not have the accumulation as described above, so as to reduce the cost of the operation. In such operations, the line speed is lowered, sometimes by a factor of ten, so that the operator can manually attach the new tape to the running tape, by means of an adhesive tape. The running tape is then manually cut after joining with the new tape, before the line speed is raised back to its normal level. However, in addition to the problems described above including the presence of an operator at the right moment and the high degree of skill and dexterity required of the operator, changing the speed of the manufacturing process may adversely affect product quality.
An embodiment of the invention is directed to an automatic tape crossover machine having two feeding mechanisms to supply running and new tapes, respectively. A powered cutter is provided through which the running tape is to pass and be cut in response to a cut signal, where the cutter is positioned downstream of the first tape feeding mechanism. The machine also includes a joining mechanism at which a portion of a new tape is to be joined to the running tape in response to a join signal. Control circuitry automatically determines that a tape exhaustion condition has been reached and asserts the join and cut signals to join the running and new tapes and to cut the running tape, before the tape feeding mechanism is emptied of the running tape. The machine thus allows the automatic transition from the running tape to the new tape, i.e. without requiring the presence or manual assistance of a human operator when joining the two tapes. In addition, the process line speed need not be altered for the crossover, thereby reducing the probability of inconsistencies in product quality.